Cruise Control Actuator - PeachParts Mercedes-Benz Forum

190D22 · #1 05-23-2002, 02:45 PM

I tested my cruise control actuator today by putting 12V on pins 4 and 5 to check the motor and 12V on pins 6 and 7 to test the selenoid. The selenoid is fine. I think the motor is dying. It doesn't sound like it's running smooth. And when I put 12V on the motor AND selenoid the arm didn't move at all. It just made a clicking sound and the arm jerked a little. (I have no throttle to actuator linkage so I wasn't giving the engine any throttle) I have yet to test the amplifier yet, I am going to get around to doing that hopefully this weekend.

Should the actuator arm should have moved when I applied voltage to the selenoid and the motor? I tried moving the arm all the way to the other side just to make sure I wasn't making it try to move it as far as it could go.

If the amp checks out OK should I get a new actuator and linkage piece?

Since I've owned this car the CC has never worked.

MikeTangas · #2 05-24-2002, 01:33 AM

When you put power to the actuator, the motor should spin with a barely audible whirring sound. Sound not make any loud clunking or grinding sounds. You need to be sure to run the actuator both directions (by reversing the power leads). Mine was so quiet I had to put my hand on the actuator to feel it spinning. Power to the solenoid should produce a solid clunk as the solenoid engages. I didn't try seeing if the arm moved, I trusted the spin and clunk. Once I replaced the amp the cruise works great.

If all is well, I'd bet on a bad amplifier.

190D22 · #3 05-25-2002, 10:47 AM

I tried the motor in both directions. It was pretty loud, compared to what you described. The selenoid made a nice clunk like it should. The motor was noisy and the arm didn't move. I also have to test the amp as well. Where exactly is mine? I was installed new front speakers yesterday and I had the kick plate off by the pedals and I didn't see anything that resembled the descriptions and pictures I've seen of CC amps. Is it located somewhere odd in the 201? Thanks for the reply.

MikeTangas · #4 05-25-2002, 12:12 PM

If your actuator is making that much noise, it probably needs to be replaced. Also, a bad actuator can fry the amp, so you'll probably be replacing that as well.

I'm not sure on the 201, but for all the other I've seen, you'll have to become a contortionist to get at the amp. It is up in the dash, you'll have to pull the lower panel (driver's side) to gain access. The amp is a fairly large silver box about 6 inches tall and 3 inches wide and will be bolted to the brake pedal pedistal. There are two electrical connections, one directly to the amp, the other to the small relay on the side of the amp. Don't separate the relay from the amp under the dash, bring them out as a set.

The amp is bolted to the pedistal with a single 10mm nut. It appears the nut is on a stub, but it really is a bolt which sits in a hexagonal recess and you will most likely knock it out of the recess unpon installing the replacement. A real PITA to get the bolt back in AND hold in place while getting the amp on the bolt. But it can be done.

Once you remove that 10mm nut, the amp should come straight down and out from under the dash.

Hope this helps.

ck42 · #5 05-25-2002, 03:18 PM

The actuator motor should pull approx. 130mA. Anything significantly higher than that CAN blowout the output transistors in the amplifier.....mine is currently pulling about 380mA; I'm sending off for a rebuilt one here very shortly.

Apparently, the actuator motor can fail in a certain way that ends up shorting the amplifier outputs....and thereby blowing-out the amplifier. This is a common failture scenario.

But, yes, the motor should be smooth and quiet.

Also, DON'T activate the solenoid AND the motor at the same time. This is NOT suppose to happen and can damage the actuator from what I understand about the unit.

#6 05-31-2002, 04:02 PM

The sound of the actuator does not always indicate its condition. When the motor spins the smallest gear always spins with it. That's generally what you hear. The current draw does matter; over 200mA is too much and can blow the output transistors in the amp. Check out http://www.gdl-online.com/testproc.html